The field of the invention is the working of metals and more particularly the shaping of the edges of a metal closure.
The invention is essentially directed to a method for sealing a metal closure on to a vessel with a beaded circular edge, combining two conditions for application in the mass production of preserves:
use of a closure blank of reduced diameter, for economy of metal;
a fast and simple method for fitting, if possible in a single operation.
The airtight sealing, by a metal closure, of a vessel the edge of which is a rigid beaded lip, is most often done by a succcession of mechanical operations the last of which is a bending back of the skirt of the closure, previously turned into the neck of the lip, in order to effect, by tightening, a durable engagement. This bending is done laterally, for example with one or more milling wheels.
In a different and simpler manner, U.S. Pat. No. 3,190,481 describes the fitting of a closure blank having a central depression which comes to rest in the mouth of a glass vessel, this blank having a U-shaped outer edge, which a curved concave pressing tool will progressively shape so that the U-shaped periphery is levered under the beaded edge of the vessel, thus effecting a fit.
In a similar manner in U.S. Pat. No. 1,625,245 an annular bevelled tool bends the edge of the cap blank and forces it under the outside rolled edge of the vessel.
Such methods appear simple; but the edge of the closure blank, comprising an outer roll, uses a significant quantity of metal or (other) material, which is a serious economic handicap.